NAME    [Toc]    [Back]

       getprotobynumber,  getprotobynumber_r  -  Get  a  protocol
       entry by number

SYNOPSIS    [Toc]    [Back]

       #include <netdb.h>

       struct protoent *getprotobynumber(
               int num );

       [Tru64 UNIX]  The following obsolete function is supported
       in  order to maintain backward compatibility with previous
       versions of the operating system.  You should not  use  it
       in new designs.  int getprotobynumber_r(
               int num,
               struct protoent *proto,
               struct protoent_data *proto_data );

LIBRARY    [Toc]    [Back]

       Standard C Library (libc)

STANDARDS    [Toc]    [Back]

       Interfaces  documented  on  this reference page conform to
       industry standards as follows:

       getprotobyname():  XNS4.0, XNS5.0

       Refer to the standards(5) reference page for more information
 about industry standards and associated tags.

PARAMETERS    [Toc]    [Back]

       Specifies  the protocol number.  [Tru64 UNIX]  For getprotobynumber_r()
 only, this points to  the  protoent  structure.
  The netdb.h header file defines the protoent structure.
  [Tru64 UNIX]  For getprotobynumber_r()  only,  this
       is  data  for  the protocols database.  The netdb.h header
       file defines the protoent_data structure.

DESCRIPTION    [Toc]    [Back]

       The getprotobynumber() function returns  a  pointer  to  a
       structure  of  type  protoent. Its members specify data in
       fields from a record line in either the local  /etc/protocols
  file  or  NIS distributed network protocols database
       file. To determine which file or files to search,  and  in
       which   order,   the  system  uses  the  switches  in  the
       /etc/svc.conf file. The netdb.h header  file  defines  the
       protoent structure.

       The  getprotobynumber() function searches the network protocols
 database file sequentially until a match  with  the
       num  parameter  occurs. The num parameter must specify the
       official  protocol  number.  When  EOF  (End-Of-File)   is
       reached  without  a  match,  a null pointer is returned by
       this function.

       When using the getprotobynumber() function, use  the  endprotoent()
 function to close the protocols file.

NOTES    [Toc]    [Back]

       The  getprotobynumber()  function  returns  a  pointer  to
       thread-specific data.   Subsequent  calls  to  this  or  a
       related function from the same thread overwrite this data.

       [Tru64  UNIX]  The  getprotobynumber_r()  function  is  an
       obsolete reentrant version of the getprotobynumber() function.
  It is supported in order to maintain backward  compatibility
  with previous versions of the operating system
       and should not be used in new designs.  Note that you must
       zero-fill the proto_data structure before its first access
       by  either  the  setprotoent_r()  or  getprotobynumber_r()
       functions.

RETURN VALUES    [Toc]    [Back]

       Upon  successful  completion, the getprotobynumber() function
 returns a pointer to a  protoent  structure.   If  it
       fails or reaches the end of the network protocols database
       file, it returns a null pointer.

       [Tru64 UNIX]  Upon successful  completion,  the  getprotobynumber_r()
 function stores the protoent structure in the
       location pointed to by proto, and returns  a  value  of  0
       (zero).  Upon failure, it returns a value of -1.

ERRORS    [Toc]    [Back]

       Current  industry standards do not define error values for
       the getprotobynumber() function.

       [Tru64 UNIX]  If any of the following  conditions  occurs,
       the getprotobynumber_r() function sets errno to the corresponding
 value:

       The proto_data or proto parameter is invalid.  The  search
       failed.

       In  addition,  if the getprotobynumber() or getprotobynumber_r()
 function fails to open the file, it sets errno  to
       indicate the cause of the failure.

FILES    [Toc]    [Back]

       The  Internet  network  protocols name database file. Each
       record in the file occupies a single line  and  has  three
       fields:  the  official protocol name, the protocol number,
       and protocol aliases.  The database service selection configuration
 file.

SEE ALSO    [Toc]    [Back]

       Functions:   getprotobyname(3),   getprotoent(3),  setprotoent(3), endprotoent(3).

       Files: protocols(4), svc.conf(4).

       Networks: nis_intro(7).

       Standards: standards(5).

       Network Programmer's Guide



                                              getprotobynumber(3)